Preparation of sulfoethyl ethers of polysaccharides



Patented Dec. 25, 1951 UNITED srArrEs NT OFFICE Hercules-Powder Company, Wilmington, DeL, incorporation-of Delaware Nd'niawing. Application March si -1949,, Serial No. 843723 15 claims. (01. zoo- 231) 1" This invention relates; to theqprepara-tionaof sulfoethyl polysa-ccharide ethers and,"more=par-- ticularly; to the'addit-ion ofvinyl sulfonic'acid' to cellulose whereby asulfoethyl cellulose isformed-.-,

Sulfoethyl cellulose is ac hydrophilic cellulose derivative having many important uses: Numerous attempts have been made to devel'op ascome mercially. feasible method of preparingisulioethylz cellulose, but without success; It has been sug gested that it be prepared by=reacting alkali cellulose with a, sodium Bahaloethylsulfonate or ethionic acid or the-anhydr-ide thereon; How-= ever-,1- the-yields obtained-,are poor, based on -theetheritying agent onlyaslow degree of substitu tion is obtained, and :inevery: case costly by-v products are produced, Attemptsrhavealso beenm'ade to prepare sulioethyl: cellulose-by reacting sodium vinyl sulfonate with alkali cellulose, but to obtain even a low yield and low degree of sub- 'stitution, it was necessary to use a strong aqueous alkali solution in order to bring about the reaction; Excessive amounts ofalkali are*required" and the reaction isextremelyinefficient. Underthese reactionconditionsthe double bond of the vinyl radical is hydrated and,-consequently,'onlyr ahsmallportion ofthe vinyl sulfonic acid isavailable for the etherification=reaction-.-

Now in accordance -.with this invention it has 1 been found that sulfoethyl ethersof 'polysaccharides such as sulfoethyl cellulose;--may be-pre-= paredbyreactingasuspension of an alkalipolysaccharide an inert organic solvent withvinyl sulfonic acid or salts or alkyl esters thereof: This new" method is advantageous over the 4 prior .art" methods in that the higher yields'and' degreeofi substitution obtained, low alkali consumption, and" the elimination of by-products' make it possible to produce "this valuable product on a commercial scale. Many other advantagesoverthe'prior art process such as uniformity of product -ease of operation, etc.,'wi11 be apparent'froni the follow-' ingdetailed description-of theprcicess s The following examples will; illustrate the "new process" for 'preparing sulfoethyl polysaccharides in accordance with this invention All parts and p ii'centages' are "by Weight unless otherw ise indicated;

Eirdmid li Cotton linters. ground to"20-'mesh' size, 36" parts, ere uspended in i100Q-palrtsfofisopropanol; and; l33p'arts'fiot a 4Q aqueous sodium hydroxide solution (fi'kmoles per anhydioglucose unit) were sad i--' 3 added, theinixture being stirred durij g man of 4915 parts of ammonium vinyl sulfonate (1 .78"moles per anhydroglucose unit) in 30 parts of water was then added and the reaction allowed:

to plroceed for 3 /2 hours at 75 C. The cellulose 5r derivative was separated from the organic solvent byjfiltration and the solids were washed thor oughly with 80% methanol. 7 The white fibers of o sulfoethyl cellulose were finallywashed with anhydrous methanol and driedat'60 C. in vacuo.

' 10 :A yield of 53.5 parts of sulfoethyl cellulose having a degree of substitution of 0.62 wa obtained. This sulfoethyl eenulose was completely soluble in water and in'aqueous alkali giving vi'scous','* color less, fiber-free solutions? Example 2 heated at 70 C. for 'one'hour:

ture over a period of 15 minutes.

with the temperatureat 70 C.,-200 parts of Water was added and the reaction was allowed to proceed for an additionalthree hours at 70. C. The product wasihenisolated and purified vas 'described in Example}. The'sulfoethyl cellulose so obtained was-in the form of white fibers, I

amounted to 3?.5 parts, andhad a degree .of substitutionof 1.03. H

Example 3 unit). The mixture was agitated and heated-at glucose unit) was added. Heating at 75 C. was continued for an additional'four hours. The sulioethyl" cellulose was isolate'd and purified-as described in-ExampleL A yield of 3.94 parts was obtainedii This sulfoethyl cellulose had a degree of 'substitutioriof"0;37 and "was highly soluble in bcthtwater and dilute aqueous alkali.

mama 4' suamggsmr'ry, was f.

tio'nafia for'anadditional hour at-C, A 'solu- '55 ql eularfequivalnts v10f.- alkaliiper anhydroglu Threespartsof cotton Enters 420 mesh) was 1 suspended in..100\ parts of dioxane and treated-- with 16.7 partsof aw40%- aqueous sodium hydroxide solution. (9 moles perl anhydroglucose cose unit) The mixture was heated for one hour at 70 C. after which 4.72 parts of solid ammonium vinyl sulfonate (2.04 molecular equivalents per anhydroglucose unit) was added. Heating was continued at 70 C. for an additional four hours and the product was isolated and purified as described in Example 1. A yield of 4.08 parts of white fibrous sulfoethyl cellulose was obtained. This material had a degree of substitution of 0.40 and was soluble in both water and dilute aqueous alkali.

Example 5 Five parts of purified wood pulp (20 mesh) was thoroughly macerated with 24.6 parts of a 30% aqueous sodium hydroxide solution (6 moles per anhydroglucose unit). The crumbs of alkali cellulose so formed were then suspended in 100 parts of isoprooanol. The slurry was agitated and heated at 70 C. for one hour. To this mixture was added a solution of 6.65 parts of vinyl sulfonic acid (2 moles per anhydroglucose unit) in 20 parts of isopropanol. Heating was continued for an additional three hours at 700 C. The product was isolated and purified as described in Example 1. A yield of 7.5 parts of white fibers having a degree of substitution of 0.62 was obtained. This product was soluble in both water and dilute aqueous alkali.

Example 6 One hundred parts of cotton linters (20 mesh) was sus ende in 2800 parts of isopropanol and treated with 308 parts of a 40% aqueous sodium hydroxi e sol tion (5 moles per anhydroglucose unitl. The slurry was agitated and heated at 70 C. for one hour. A solution of 38.5 parts of ammonium vinyl sulfonate (0.5 mole per anhydroglucose unitl in 200 parts of water was added and heat ng at 75 C. was continued for four ho rs. The fibro s product was isolated and purified as described in Eyam le 1. A yield of 111 parts was obtained. This sulfoethyl cellulose had a de ree of s bstitution of 0.21 and was soluble in dilute alkali.

Example 7 Ten parts of cotton linters (20 mesh) was treated with 25 parts of a 36% aqueo s sodi m hydroxide/solution (3.58 m les per anhydroglucose unit). The alkali cellulose so formed was reflu ed in dry dioxane for onealf hour after which 35 parts of n-propyl vinyl sulfonate (3.0 moles per anhvdroglucose unit) was added and the reaction mixture was a itated and heated at 105 C. for four hours. The sulfoethyl cellulose so obtained was separated from the liquid medium by filtration and washed with methanol, acetone, and finally hexane. It was found to contain 0.175 sulfoethyl group per glucose unit, was 1slightly soluble in water and soluble in dilute a a 1.

Example 8 Five parts of a purified corn starch was suspended in 80 parts of isopropanol and treated with 18.5 parts of a 40% aqueous sodium hydroxide solution (6 moles per anhydroglucose unit). The slurry was heated for one hour .at 70 C. and then 3.85 parts of solid ammonium vinyl sulfonate (1.0 mole per anhydroglucose unit) was added. The slurry was agitated and heating at 70 C. was continued for five hours. The product was separated from the organic solvent by filtration, washed with 80% methanol and then with anhydrous methanol and finally was drledjat 4 C. in vacuo. A yield of 6.04 parts of the sulfoethyl ether of starch having a degree of substitution of 0.48 was obtained. The product was a white powder which was soluble in water and in dilute aqueous alkali yielding viscous solutions.

The product prepared by the above procedures relating to cellulosic materials is in the form of the alkali salt of the sulfoethyl cellulose. If the free acid is desired, it may be acidified by the addition of a mineral acid. The free acid form of sulfoethyl cellulose is a white, finely fibrous material, which at substitutions of 0.2 and above is markedly hydrophilic. It has the same solubility characteristics as the alkali salts of the sulfoethyl cellulose. The following example illustrates the preparation of the free acid form of sulfoethyl cellulose.

Example 9 vOne part of sodium sulfoethyl cellulose was agitated for five hours at room temperature in 20 parts of 75% aqueous methanol containing two parts of concentrated hydrochloric acid. The acid liquor was then drained ofi and the resultant free acid form of sulfoethyl cellulose was washed with methanol, then with anhydrous methanol and finally was dried in vacuo at room temperature. It was soluble in both water and dilute alkali.

In accordance with this invention, sulfoethyl ethers of polysaccharides may be prepared by the addition of vinyl sulfonic acid to the polysaccharide in an inert organic solvent medium and in the presence of an alkaline reagent. The reaction, using cellulose as a typical polysaccharide, I

may be represented as follows:

MOH

sulfonic acid itself ma be used or a salt thereof such as the alkali metal salts, ammonium salt, quaternary ammonium salt, etc., or an alkyl ester of vinyl sulfonic acid such as the methyl, ethyl, etc. esters may be used. In the latter case the ester group is hydrolyzed in the presence of the alkali, and alcohol is obtained as a lay-product. The vinyl sulfonate may be added as such, in solid form in the case of the salts, or liquid form in the case of the free acid or esters thereof, or it may be added as a solution in water or in some other solvent. If it is added in the form of an aqueous solution, the volume of water used should be such that the amount of water in the reaction mixture does not exceed about 15% of the total liquid phase and preferably amounts to not salt) to be added to the polysaccharide material 7 dependent upon. the degree of etherification desiredtinctherfinal: roducta, Usuallwtosobtain-rz; butanol eti-ahydrotura .ethylenaslycol-.diethylsi' a. .waterand alkali-soluble isulioethy thersrofz; ether,v tc Bestxresultsar obtaine'clzrwitli-organica acazpolys'accharide ufroma about'izflb: to: about 2'1) sohientsiat ateareswaterirsolublessuchyassisopro1 molecularzequivalents 1otithe1-vinykfisulfonatecare pancL'tdioxane etca Imthese'zmcdia watencan'not added"pen'etherifiablehydroxyl groupinth'eapol r accuinulateni ztheiacellulose:derivative: phasetof saccharide'r; Largeraamountssmay b'etusedaif' deer the reactio mint-urea I-Ioweversthc.suifoethylaa sired, without any disadvantageous result How= tion eaction maybesatisfactorily:carried rfout. in ever; when lssersr'amountsrare used-,1, the; final such Water-insolublerorganic1solvents;as:benzene: produpt maymotbeesuflicientlytetherifiedtmproe toluene, et'c'ii. 'I'he'- polysaccharidesmayi-be sus. ducezthe water:- antitalkaliisoluble g'characteristics zirl'o pende he i solvent-.ibefore 'the treatment with which areades'ireds th'e ai a me -r'eag'ent; orathe alkali i'cellulc'se"may= 'Therreaction"between:thecapolysaccharidecasi be prepared and themsuspendedi-irr thGF-SOIVEHEI for example, cellulose and the vinyl sulfonic'acidi 'lli'e amount ofisolvent used 'isxdetermined by the takes eplacein 'the presencemt an alkalinesreagent. type of agitation available for the heterogeneous. Any:strongly' ialkaline' hydroxide such :as,'-=-ior1;ex-'- is' i'eactbnn s'iiioe miningmeoomesincreasingly .difample}: theszaikaliiimetaishydroxides ZSUGlIlEfiSIgSO-3=- fiiiuit withtincreasing cellulose proportions; and 1 dinimorznotassiuimhydroxide,; r;-the.zquaternary, ie=form of=cellulose used;/i.e.=', ammonium hydroxidesrsuchr:as'ttrimethylbenzyl 'uicdivisiom- In-general', with "ground. 1 annnoniunr;hydroxide;etcizxmayrbe:usedzi- The cotton liiiters-,-:acelli1lose to solvent ratio of about alkalinezreagentsarei believed:totservectworpur z'c' lr iwto about -'1:25*-is- 'used"iand with unground? poses'in: the sulroethylationrreaction;.toi'swell and linters, a ratio of about 1 :25 to about 1250 is used.

disperse :the;* cellulose tort other polysaecharide', The' rea'cti'o'n in: accordance' with this 'inventhuszactiriatingdt, and'to catalyze thewin-ylxsultion is' carried but 'atatemperatureof from-about fonate addition. 50 to -abbut"-1 I0 '"C* 'and preferably ata tempera- Any moder-of:rintroducing::the alkaline-:;reagent as tture o'f "about -65* to about 90"'C; If 'th'e-pa'rinrthea'eactionmiixture maybe-.utilizeda The 'eelticular solv'ent Eingmsed-as:the diluent in -th'e lu'loselor polysaccharideimay the converted ,to an reactiomposses'ses a b'oiling pointbel'o'w this temalkalincellulose-ror polysaccharide-*by;suspending perature rangeii the reaction may b'e carried out it in an: organic :solvent"and itreatingithe slurry underpr'essure as in-"an autoclave; The tam-'- with anmqueoussolution-offromzzo,to-.80%s' consoeperature of the suspension of alkali cellulose in centrationzofithe -alkalinereagent: In this alkali-.1 crganic ==solvent is preferably adjusted "to" the 08111110518 pr parationgthe-amounto alk line r a rea'ction temperalturepridr to' the vinyl "suli'o'nate gene-zaddewis adjustedtmapprOXimatQIy l 1170 5.5 additiona Followingthe vinyl ='s'ulfonate 1 addi molecular equivalents-:zper anhydr'oglucose --unit,v mona tic-1ereaction is ailow d to p ail'fe' whenvan alkalisalttofvtheavinylrsulfonicracid is 33 ii d-tmneraturefor =fr om==1 to fi hours'and to- -be used'.. Howevenqwhenxrfreeevinyl:sulfonica preferably ffOn'Pabbll 2 /2to 4'- h0urs'.-' Lo ger" acid, ammonium-vinylsulfonate or 'anialiryl vinyl reaction times may be used but it is believed sulfonate is to: :be 111866.; A the alkali proportion is i: t 0 dv ta es am -reali ed from reaction increased-i:by --anaamountasufficient-to'wformwthea m sfi gr aterthan ours 'and;in'fa'ctyabove alkali?) saltr-of' theqfreez acidi-w The -reactio1'1 pro- 4%. depolymerization ceeds'favorably iW-it-h higherprop'ortionsof alkali nd de-ether ifidationc beg 'li be oticeable. but-to For-event side-reactions;-sueh-as 'ytheihydra-w THE f 3 fi may take place *in tioirxofathe -:-:vinyl ldoublewbonmzthe alkali;- conless tha'r i one hour buts u y 110 a "r act n" centiiation is'z pr'eferabl'y wit-hint :therange-of; 4?.to1 isrinofi BfiifinFOn thi'ibasigwfill/my]; lslilfdnate 5.5 molecular equivalents. The mixture oficel c s n" luose'gzor'scellulose t=derivative, or other polysacfi i' w pr p edm, accharide organic olvent and alkaline reagent is corda'nce with this inventio'nis readily-isolated then agitated andrheated for one hour at 50 C. from the-zreaction-=mixtiire $"fiitfat b y on above or N be .at room 0f -Sepalatillg L I temperature. An alternative method ofaalkaliws'ei Iii-"may polysaccharide formation consists of jpretreating fifidftby iw'ashiifigdthefibrous, pl'dductj-tdirmove'i the carbohydratamaterial Withanaqueous alalkali d any unreacte'd 'vinylsulfonate; Any Recliner-reagent and then suspending the crumbs; cbnvemenwsolvent'-fr"thiS"TWa$/hifigOperation so zformedrin an. organicv solvent before the su1f0= maydblisedigwfiicfi sbllientiwfllynot dissolve f' ethfylatiom'reaction; Substantially @the sameftre-l re e bttiwhich win' dissolve:the

By" alkalijmellulose .or .other'cpolysaccharidizas metfianbt'isohltidhs h ol h'as used ins-this specification and'appended claimsz-is beemfmnwtqbe e' material for can? meant the alkalimetalsaltsland-ammonium salts mg thisiiWaSh-ingh operation?" If thelfrgeel as, for example, the quaternary ammonium salts ;acidz'iformi-of ithe @sulfoethylcellulose'zis :desired of themarbohydrate rath'enth'anwtheralkaliysalt, .the alkali saltrofthez The rea'etion-between-the allali cellulose; 01 SmfethyL1m1e"mayibeisuspended finial-cont other pclysacbha gide a ndfith ifi ly lf icf id venient i'liqlldit dllllBIlt:-;SHCII as:::m,ethanol,; antlziv in accordance with this invention is carried out acidified by the addition of a mineral acid- The in the presence of an organic solvent or- L13 fibrous acid fOrm 0f the sulfOefihyl 0811111058 may garlic 1 m may be used as t medium for then be washed as in the case of the alkali salt. the sulfoethylation reaction, provided that it is The fibers f Sulfoethyl cellulose a i Salt inert under the reaction conditions, i. e., does not of sulfoethyl 081111105 m y then be dried y a y react with the vinyl sulfonate. The main funcdesirable means. tions of the organic solvent are to serve as a 1*?) The process of preparing sulfoethyl polysacheat transfer medium, and as a dispersing or charides by reacting a suspension of an alkali insolubilizing agent so that the hydrophilic depolysaccharide in an inert organic solvent with rivative will remain in a finely fibrous condition. vinyl sulfonic acid in accordance with this in- Suitable organic solvents which may be used for vention makes possible the commercial produc the reaction are dioxane, isopropanol, tertiary tion of the sulfoethyl ethers of polysaccharides.

The new process is an eflicient one resulting in high yields and the alkali requirements are low in comparison with the prior art processes. The

vinyl sulfonic acid reagent is more readily'and intimately mixed with the alkali cellulose or other polysaccharide resulting in a more homogeneous ;product. Furthermore, the dimcult precipitation sisting of vinyl sulfonic acid, salts and alkyl esters thereof to a temperature of from about 50 C. to about 110 C.

2. The process of preparing a sulfoethyl ether of a polysaccharide which comprises reacting the polysaccharide with an aqueous solution of a strongly basic hydroxide and then heating a suspension of the alkali polysaccharide in an inert organic solvent with one of the group consisting of vinyl sulfonic acid, salts and alkyl esters thereof to a temperature of from about 50 C. to about 110 C.

3. The process of preparing a sulfoethyl ether of cellulose which comprises heating a suspension of an alkali cellulose in an inert organic solvent with one of the group consisting of vinyl sulfonic acid, salts and alkyl esters thereof to a temperature of from about 50 C. to about 110 C.

4. The process of preparing a sulfoethyl ether of cellulose which comprises reacting the cellulose with an aqueous solution of a strongly basic hydroxide and then heating a suspension of the alkali cellulose in an inert organic solvent with one of the group consisting of vinyl sulfonic acid,

salts and alkyl esters thereof to a temperature of from about 50 C. to about 110 C.

5. The process of preparing a sulfoethyl ether of cellulose which comprises reacting the cellulose with an aqueous solution of a strongly basic hydroxide and then heating suspension of the alkali cellulose in an inert organic solvent with vinyl sulfonic acid to a temperature of from about 50 C. to about 110 C.

6. The process of preparing a sulfoethyl ether /step necessary to isolate the product is elimialkali cellulose in an inert organic solvent with a salt of vinyl sulfonic acid. Y

8. The process of preparing a sulfoethyl ether of cellulose which comprises heating a suspension. of an alkali cellulose in an inert organic solvent with vinyl sulfonic acid to a temperature of from about 50 C. to about 110 C.

'9. The process of preparing a sulfoethyl ether of cellulose which comprises heating a suspension of an alkali cellulose in an inert organic solvent with an alkyl ester of vinyl sulfonic acid to a temperature of from about 50 C. to about 110 C. 10. The process of preparing a sulfoethyl ethe of cellulose which comprises heating a suspension of an alkali cellulose in an inert organic solvent with a salt of vinyl sulfonic acid to a temperature of from about 50 C. to about 110 C.

11. The process of preparing a sulfoethyl ether I.

12. The process of preparing a sulfoethyl ether of cellulose which comprises heating a suspension of an alkali cellulose'in an inert organic solvent with ammonium vinyl sulfonate to a temperature of from about 50 C. to about 110 C.

13. The process of preparing a sulfoethyl ether of cellulose which comprises heating a suspension of an alkali cellulose in an inert organic solvent with vinyl sulfonic acid to a temperature of from about C. to about C.

14. The process of preparing a sulfoethyl ether of cellulose which comprises heating a suspension of an alkali cellulose in an inert organic solvent with ammonium vinyl sulfonate to a temperature of from about 65 C. to about 90 C.

15. The process of preparing a sulfoethyl ether of cellulose which comprises heating a suspension of an alkali cellulose in an inert organic solvent with an alkali metal salt of vinyl sulfonic acid to a temperature of from about 65 C. to about'90" C.

VERNON R. GRASSIE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Great Britain June 15, 1942 I 

15. THE PROCESS OF PREPARING A SULFONETHYL ETHER OF CELLULOSE WHICH COMPRISES HEATING A SUSPENSION OF AN ALKALI CELLULOSE IN AN INERT ORGANIC SOLVENT WITH AN ALKALI METAL SALT OF VINYL SULFONIC ACID TO A TEMPERATURE OF FROM ABOUT 65* C. TO ABOUT 90* C. 